Experimental Study And Finite Element Analysis On The Connections Of Multibarrel Tube-confined Concrete Column

Concrete filled steel tube (CFST) structures are widely used in many countries due to its high bearing capacity, good ductility, high toughness, fire resistance, and good seismic performance. However, the researches on the mechanical properties for the connections of CFST are still relatively limited. Although a large number of experimental studies have been carried out, and the theoretical analysis of mechanical properties for the connections are still not deep enough. The researches for the connections of CFST mainly focused on connections with steel beams. However, the investigations for connections with reinforced concrete (RC) beams are very few.In this paper, the advances of the connections of CFST have been reviewed firstly. And the behavior of a new type of the connections for Multibarrel tube-confined concrete column with RC ring beam has been studied, the main content includes:(1)The new type of connections for the Multibarrel CFST column and RC ring beam is that the outer tube of the Multibarrel CFST disconnected in the connections, the longitudinal reinforcement of RC beam inserted directly into the nodes. In this paper, the pseudo-static tests on four connections have been carried out. The FEM models have been established and the behaviors of connections have been numerical simulated.(2)The behaviors of connections under low cyclic loadings have been investigated in this paper. The failure patterns and the failure mechanism have been analysed. The plastic hinges were formed at the ring beams and the failure of the test specimens is ductile. The hysteretic curves of load-displacement, the relationship between moment and relative angle of the beams and the columns, the ultimate bearing capacity and the skeleton curves are obtained in this paper. And the restoring force model for the new type connections of RC ring beams with the discontinuous outer Tubes is finally established.(3)The software ANSYS of finite element was used to simulate the behavior of connections. The simulated hysteretic curves were compared with experimental data and good agreement can be observed. Moreover, parametric studied have been carried out to investigate the influences of anchorage length of vertical steel bars for the nodes area, the strength of the concrete for the nodes area, the concrete strength of the frame beam, and the longitudinal reinforcement ratio of the frame beam on the skeleton curves.